1. Field of the Invention
This invention relates to reactors, such as rotary kilns, for the treatment of a tumbling bed of mix sized pulverulent material and particularly to ports in the kiln shell for discharging gases such as fuel, steam and/or air to the interior of a rotary kiln wherein the port is resistant to plugging and self-purging of the pulverulent material.
2. Description of the Prior Art
In the prior art, rotary kilns are known wherein a plurality of ports are provided through the shell of the kiln to admit air and fuel into the interior of the kiln. Examples of such prior art kilns are disclosed in U.S. Pat. Nos. 1,216,667; 2,091,850 and 3,182,980. Nozzles for such kilns are disclosed in U.S. Pat. Nos. 3,794,483; 3,946,949 and 4,214,707. Mechanisms for operating such nozzles are disclosed in U.S. Pat. Nos. 3,847,538 and 4,070,149.
In certain of the prior art, e.g., U.S. Pat. Nos. 1,216,667 and 2,091,850 kiln fuel and/or air is injected into the kiln through ports while the ports are below the material charge of the bed. In the other of the aforesaid prior patents, air and such as a fuel gas is injected alternately with the fuel gas being injected when the ports are beneath the bed of the material charge and air being injected when the ports are over the bed. With the aforesaid apparatus operated to process mixed size materials, the smaller particles may enter the ports and associated piping impairing the flow of fluid through the ports and eventually causing complete clogging of the port, rendering it useless for under bed fluid injection.
Additionally, while such rotary kilns may have as many as 600 nozzles, commonly five or more of the nozzles are activated by a single valve. Consequently, if material particles enter the associated piping through any one port and damage a valve, numerous ports will become inoperative. This is particularly troublesome where a port is normally inactive and makes numerous passes beneath a bed of material with no gas passing through the port or associated piping. Thus, when a port or number of ports become useless by reason of being plugged or by damage to an associated control valve, the capacity of the kiln is reduced and its operational time span between maintenance periods is reduced.
A more recent U.S. patent, U.S. Pat. No. 4,214,707 to Flaherty dated July 19, 1980 discloses a self-purging port for a rotary kiln. In the Flaherty patent, the port has a nozzle having a plurality of orifices for passing fluid to the interior of a kiln. Behind the nozzle is a labyrinth trap. Particulates from the kiln are allowed to pass through the nozzle orifices into the trap as the port passes beneath material in the kiln. A plurality of orifices in the trap causes fluid to swirl as the fluid passes through the trap on its way to the interior of the kiln. This swirling causes the fluid to pick up the particulates in the trap and carry them into the kiln.
It is the general object of the present invention to provide a further improved port construction which is resistant to plugging and easily purged by flowing fluids.
Another object of the present invention is to provide a port which successively screens particulate matter thereby achieving a substantial reduction in the quantity of particulates entering the port body as well as flushing out particulates that do enter the port body.
Still another object of the present invention is to provide a port comprising a plurality of particulate screening mechanisms where each screening mechanism within the port acts independently of the other mechanisms to readily permit scaling up the port design and whereby plugging of one mechanism does not result in the loss of an entire port.